Normally, but not exclusively, when I call something a project, it’s either a setting (a “period”, if I must use that inadequate word) in a specific scale and scope, or an undertaking to build terrain/scenery to fully represent some category of location (such as jungle or urban ruins). For the most part, these are not projects that are meant to end, though they are meant to reach a state of adequacy sooner or later. Ending a project implies killing the creative side of it. I’ll usually want to leave my projects open for new ideas and opportunities that may arise later.
In this context, I’m not concerned with the true meaning of the word “project”. I just go by established conventions of jargon in the hobby, e.g. “Andy’s Star Trek project” or “Julie’s dungeon project”.
Nothing of this is exclusive of other definitions of the word. No reason that rebasing and touching up some old figures can’t be called a project.